Annual Water Budget for Hava Soil Series
by Madison Walter
October 26th, 2018
Average monthly precipitation for the Hava soil series fluctuates between 36 and 325 mm, peaking in November. Meanwhile evapotranspiration varies between 21 and 117 mm, peaking in July.
Should drought affect this soil, the effects would be extreme due to the fact that the Hava does not usually experience deficit. Based on the principles outlined in our textbook, I would attempt to mitigate the effects of a drought situation by encouraging plant growth in the soil so that the roots of these organisms could help hold water in the soil and prevent runoff loss of precipitation.
Sources:
Brady, N. C., & Weil, R. R. (2010). Elements of the nature and properties of soils.
Hava Soil Plant Available Water
by: Madison Walter
October 19th, 2018
This post describes the plant available water in the Hava soil series, located in Elwha, WA. According to the SoilWeb description of the Hava, plant roots occur in the upper four horizons, excluding the two uppermost O horizons. The following table shows the values needed and the results of calculating plant available water for these horizons.
The depth of plant available water was calculated here by first subtracting permanent wilting point values from field capacity values, obtained from an online texture calculator, to obtain percentage of plant available water. This percentage was then multiplied by the depth of each horizon to obtain the value in centimeters. All of the depths for each horizon were added together to obtain the total. The calculations for each horizon are listed below:
A horizon
.2167-.1087=.1080
15.24 cm x .1080= 1.6459 cm
Bw1 horizon
.2167-.1087=.1080
71.78 cm x .1080= 7.7522 cm
Bw2 horizon
.2167-.1087=.1080
20.32 cm x .1080= 2.1945 cm
BC horizon
.2167-.1087=.1080
53.34 cm x .089= 5.686 cm
Total:
1.6459 + 7.7522 + 2.1945 + 5.686 = 17.2786 cm
The online calculator used to obtain the field capacity and permanent wilting point values that these calculations are based on does not take into account the coarse fragment percentage of the soil or the amount of organic matter in the soil. All of the horizons for which calculations were made have coarse fragment percentages between 60 and 75%. These high values may cause the plant available water calculations to be off because rocks reduce a soil’s water holding capacity by reducing surface area. The calculator also did not take into account the Hava soil’s high organic matter content, exemplified by the presence of the two O horizons, which also may skew the plant available water values due to the tendency of organic matter to increase the amount of plant available water in a soil.
Sources:
Saxton, K. E., Dr. (1997, February 18). Soil Texture Triangle: Hydraulic Properties Calculator. Retrieved October 17, 2018, from
http://resources.hwb.wales.gov.uk/VTC/env-sci/module2/soils/soilwatr.htm
SoilWeb: Hava Series. (2004). Retrieved from https://casoilresource.lawr.ucdavis.edu/gmap/
Plant Available Water by Keara Mulvaney
Calculations:
PAW = FC – PWP
Horizon Oi:
PAW: 0.231 – 0.129 = 0.102
0.102 % water (7.62 cm) = 0.777 cm3 H2O/cm3 soil
Horizon A:
0.187 – 0.0882 = 0.0988
0.0988 % water (22.86 cm) = 2.26 cm3 H2O/cm3 soil
Horizons Bs1, Bs2, and Bs3:
0.162 – 0.0650 = 0.097
0.0970 % water (35.56 cm) = 3.45 cm3 H2O/cm3 soil
Total PAW:
0.777+2.26+3.45+3.45+3.45= 13.387 cm3 H2O/cm3 soil
The Welsh triangle estimates FC and PWP based on texture. However, it does not take into account rocks and soil organic matter. These factors could change the PAW in the Bullards Soil Series. Rocks take up surface area and decrease the PAW of a soil. This soil series has relatively low rock fragments starting with 0% in the Oi horizon and increasing gradually until it reaches 25% in horizon Bs3. Organic matter increases the PAW of a soil. This soil series has some organic matter in the Oi horizon but overall does not have a great amount of organic matter.
Saxton, K. E., Dr. (1997, February 18). Soil Texture Triangle: Hydraulic Properties Calculator. Retrieved October 17, 2018, from
http://resources.hwb.wales.gov.uk/VTC/env-sci/module2/soils/soilwatr.htm
Paxton Soil Plant Available Water (by: Grace Larsen, Oct 17, 2018)
Greetings, fellow soil ninjas!! Today we will be looking at the plant available water in Paxton soil. This particular profile in Newtown, CT has roots in the uppermost three horizons – Ap, Bw1, and Bw2. We will calculate the plant available water (PAW) for each of these horizons below:
The uppermost three horizons of Paxton soil, where the root zone is located, have a very low percentage of rock content (between 5 -10%). Rock fragments, unlike soil, are unable to hold plant available water, therefore decreasing the amount of PAW that the root-zone horizons of the profile can hold. In this particular profile of Paxton, the small percentage of rocks indicates that the calculated plant available water is likely close to accurate, as there are not many rocks in the equation that would lower the PAW capacity of the soil. The upper horizon of the Paxton soil profile (Ap) is heavily covered with organic material, which may increase the plant available water because more water is made easily available to plants due to improved aggregation.
Sources Cited:
Saxton, K. E., Dr. (1997, February 18). Soil Texture Triangle: Hydraulic Properties Calculator. Retrieved October 17, 2018, from
http://resources.hwb.wales.gov.uk/VTC/env-sci/module2/soils/soilwatr.htm
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